feat: setting permission mask in Entry and Archive

[weihanglo]

This is convenience when you want to disable some permission bits
during unpacking. Currently only support Unix.

[weihanglo]

Another solution is that we can have a set_mask() function to set mask. It might also be useful when a user just wants to remove some permissions.

[joshtriplett]

@weihanglo I would suggest splitting the UNC path fix into a separate PR?

And I do think mask would be more convenient than mode, since then tar can still handle "executable or not" itself.

[weihanglo]

Thanks @joshtriplett. #331 has been created for UNC path fix.

And this PR is also switched to set_mask from set_mode. I am not sure about how that works on Windows though.

[alexcrichton]

Thanks! Right now the mask looks like it's inverted when applying against a mode, so could that be documented? Either that or could the mask not be inverted and the default mask is u32::MAX?

[weihanglo]

Thanks for the review! I went ahead with a logical notation. If you like not inverted one please let me know :)

[weihanglo]

Thank you so much Alex! Just a little wish: Could we have a new release for the latest patches? :)

[alexcrichton]

Sorry for the delay, but sure yeah published now.